iOS FFmpeg+x264 编码

本文介绍iOS下使用FFmpeg+x264进行软编码。
x264是一个开源的H.264/MPEG-4 AVC视频编码函数库，我们可以直接使用x264的API进行编码，也可以将x264编译到FFmpeg中，使用FFmpeg提供的API进行编码。

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一、编译x264

1、下载gas-preprocessor文件：

• https://github.com/libav/gas-preprocessor
• 将里面的gas-preprocessor.pl拷贝到/usr/local/bin目录下
• 修改文件权限：chmod 777 /usr/local/bin/gas-preprocessor.pl

gas-preprocessor

2、下载x264源码：

• [https://www.videolan.org/developers/x264.html] x264-snapshot

3、下载x264编译脚本文件：

• https://www.videolan.org/developers/x264.html
  build-x264.sh

4、将源码与脚本放在一起：

• 新建一个文件夹，将编译脚本build-x264.sh与x264源码文件夹放入这个新建文件夹中，并将x264文件夹(x264-snapshot-xxxx)改名为"x264"

  
  x264源码文件与x264编译脚本

5、修改权限、执行脚本：

• sudo chmod u+x build-x264.sh
• sudo ./build-x264.sh
• 编译过程中会生成scratch-x264文件夹与thin-x264文件夹

编译中

• 编译完成最终会生成"x264-iOS"文件夹

x264-iOS

6、编译遇到的问题：

• No working C compiler found.
  可能是xcode路径问题，终端输入命令：
  sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer/

• Found no assembler,Minimum version is yasm-x.x.x
  或Found no assembler,Minimum version is nasm-x.x.x
  或Found yasm x.x.x.xxxx,Minimum version is yasm-x.x.x
  或Found nasm x.x.x.xxxx,Minimum version is nasm-x.x.x
  原因是没有安装yasm/nasm或yasm/nasm版本太低，需要重新安装yasm/nasm。
  安装yasm/nasm可通过Homebrew安装，Homebrew下载地址：https://brew.sh/
  Homebrew安装yasm命令：brew install yasm
  Homebrew安装nasm命令：brew install nasm

• 如果已经安装了yasm/nasm并且是最新版本，仍然提示上面的问题，那么可能是yasm/nasm安装的路径没有识别到，which yasm或which nasm查看下路径，并将最新版本的yasm/nasm拷贝到此目录下，如果使用"sudo"命令也没有权限，那么需要按照下面的步骤关闭rootless：
  (1) 关机、重启进入恢复模式
  重启系统。按住Command + R进入恢复模式， 在菜单中打开Terminal
  (2) 关闭rootless
  输入：csrutil disable，重启设备
  (3) 拷贝完成，重新打开rootless

• 如果编译i386遇到No working C compiler found
  可以直接将i386略过编译，即编译脚本中ARCHS="arm64 x86_64 i386 armv7 armv7s"将i386去掉重新编译，或终端输入./build-x264.sh arm64 x86_64 armv7 armv7s进行编译

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二、编译FFmpeg+x264

1、下载FFmpeg编译脚本：

• https://github.com/kewlbear/FFmpeg-iOS-build-script
  FFmpeg-iOS-build-script-master

2、x264修改

• 将build-ffmpeg.sh中的#X264=`pwd`/fat-x264注释去掉，即X264=`pwd`/fat-x264
  X264=`pwd`/fat-x264
• 将x264编译出来的lib库文件夹放入ffmpeg编译脚本的文件夹中，并改名为"fat-x264"

fat-x264

3、编译FFmpeg

• ./build-ffmpeg.sh
  注：如果出现i386问题，脚本中同样将ARCHS中的i386去掉
  ARCHS="arm64 armv7 x86_64"
• 编译完成，在目录下会生成"FFmpeg-iOS"文件夹

FFmpeg-iOS

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三、编码实现

1、将编译好的FFmpeg-iOS与x264-iOS导入工程中

lib

2、导入系统库

• 导入<VideoToolbox/VideoToolbox.h>、libz.1.2.5.tbd、libbz2.1.0.tbd、libiconv.2.4.0.tbd等系统库
  可参考：https://www.jianshu.com/p/5d20e2a50faa

3、Code

• X264Encoder.h

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface X264Encoder : NSObject
@property (assign, nonatomic) CGSize videoSize;
@property (assign, nonatomic) CGFloat frameRate;
@property (assign, nonatomic) CGFloat maxKeyframeInterval;
@property (assign, nonatomic) CGFloat bitrate;
@property (strong, nonatomic) NSString *profileLevel;
+ (instancetype)defaultX264Encoder;
- (instancetype)initX264Encoder:(CGSize)videoSize
                                 frameRate:(NSUInteger)frameRate
                       maxKeyframeInterval:(CGFloat)maxKeyframeInterval
                                   bitrate:(NSUInteger)bitrate
                              profileLevel:(NSString *)profileLevel;
- (void)encoding:(CVPixelBufferRef)pixelBuffer timestamp:(CGFloat)timestamp;
- (void)teardown;
@end

NS_ASSUME_NONNULL_END

• X264Encoder.m

#import "X264Encoder.h"
#ifdef __cplusplus
extern "C" {
#endif
#include <libavutil/opt.h>
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#ifdef __cplusplus
};
#endif

@implementation X264Encoder
{
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVPacket packet;
    AVFrame *pFrame;
    int pictureSize;
    int frameCounter;
    int frameWidth;
    int frameHeight;
}
    
+ (instancetype)defaultX264Encoder
{
    X264Encoder *x264encoder = [[X264Encoder alloc] initX264Encoder:CGSizeMake(720, 1280) frameRate:30 maxKeyframeInterval:25 bitrate:1024*1000 profileLevel:@""];
    return x264encoder;
}

- (instancetype)initX264Encoder:(CGSize)videoSize
                      frameRate:(NSUInteger)frameRate
            maxKeyframeInterval:(CGFloat)maxKeyframeInterval
                        bitrate:(NSUInteger)bitrate
                   profileLevel:(NSString *)profileLevel
{
    self = [super init];
    if (self) {
        _videoSize = videoSize;
        _frameRate = frameRate;
        _maxKeyframeInterval = maxKeyframeInterval;
        _bitrate = bitrate;
        _profileLevel = profileLevel;
        [self setupEncoder];
    }
    return self;
}
    
- (void)setupEncoder
{
    avcodec_register_all();
    frameCounter = 0;
    frameWidth = self.videoSize.width;
    frameHeight = self.videoSize.height;
    // Param that must set
    pCodecCtx = avcodec_alloc_context3(pCodec);
    pCodecCtx->codec_id = AV_CODEC_ID_H264;
    pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
    pCodecCtx->pix_fmt = AV_PIX_FMT_YUV420P;
    pCodecCtx->width = frameWidth;
    pCodecCtx->height = frameHeight;
    pCodecCtx->time_base.num = 1;
    pCodecCtx->time_base.den = self.frameRate;
    pCodecCtx->bit_rate = self.bitrate;
    pCodecCtx->gop_size = self.maxKeyframeInterval;
    pCodecCtx->qmin = 10;
    pCodecCtx->qmax = 51;
    AVDictionary *param = NULL;
    if(pCodecCtx->codec_id == AV_CODEC_ID_H264) {
        av_dict_set(&param, "preset", "slow", 0);
        av_dict_set(&param, "tune", "zerolatency", 0);
    }
    pCodec = avcodec_find_encoder(pCodecCtx->codec_id);
    if (!pCodec) {
        NSLog(@"Can not find encoder!");
    }
    if (avcodec_open2(pCodecCtx, pCodec, &param) < 0) {
        NSLog(@"Failed to open encoder!");
    }
    pFrame = av_frame_alloc();
    pFrame->width = frameWidth;
    pFrame->height = frameHeight;
    pFrame->format = AV_PIX_FMT_YUV420P;
    avpicture_fill((AVPicture *)pFrame, NULL, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    pictureSize = avpicture_get_size(pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height);
    av_new_packet(&packet, pictureSize);
}

- (void)encoding:(CVPixelBufferRef)pixelBuffer timestamp:(CGFloat)timestamp
{
    CVPixelBufferLockBaseAddress(pixelBuffer, 0);
    UInt8 *pY = (UInt8 *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 0);
    UInt8 *pUV = (UInt8 *)CVPixelBufferGetBaseAddressOfPlane(pixelBuffer, 1);
    size_t width = CVPixelBufferGetWidth(pixelBuffer);
    size_t height = CVPixelBufferGetHeight(pixelBuffer);
    size_t pYBytes = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 0);
    size_t pUVBytes = CVPixelBufferGetBytesPerRowOfPlane(pixelBuffer, 1);
    UInt8 *pYUV420P = (UInt8 *)malloc(width * height * 3 / 2);
    UInt8 *pU = pYUV420P + (width * height);
    UInt8 *pV = pU + (width * height / 4);
    for(int i = 0; i < height; i++) {
        memcpy(pYUV420P + i * width, pY + i * pYBytes, width);
    }
    for(int j = 0; j < height / 2; j++) {
        for(int i = 0; i < width / 2; i++) {
            *(pU++) = pUV[i<<1];
            *(pV++) = pUV[(i<<1) + 1];
        }
        pUV += pUVBytes;
    }
    pFrame->data[0] = pYUV420P;
    pFrame->data[1] = pFrame->data[0] + width * height;
    pFrame->data[2] = pFrame->data[1] + (width * height) / 4;
    pFrame->pts = frameCounter;
    int got_picture = 0;
    if (!pCodecCtx) {
        CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
        return;
    }
    int ret = avcodec_encode_video2(pCodecCtx, &packet, pFrame, &got_picture);
    if(ret < 0) {
        NSLog(@"Failed to encode!");
    }
    if (got_picture == 1) {
        NSLog(@"Succeed to encode frame: %5d\tsize:%5d", frameCounter, packet.size);
        frameCounter++;
        av_free_packet(&packet);
    }
    free(pYUV420P);
    CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);
}

- (void)teardown
{
    avcodec_close(pCodecCtx);
    av_free(pFrame);
    pCodecCtx = NULL;
    pFrame = NULL;
}

@end

• use

- (void)initX264Encoder
{
    dispatch_sync(encodeQueue, ^{
        self->x264encoder = [X264Encoder defaultX264Encoder];
    });
}

- (void)teardown
{
    dispatch_sync(encodeQueue, ^{
        [self->x264encoder teardown];
    });
}
    
- (void)videoWithSampleBuffer:(CMSampleBufferRef)sampleBuffer
{
    dispatch_sync(encodeQueue, ^{
        if (self->isRecording) {
            CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
            CMTime ptsTime = CMSampleBufferGetOutputPresentationTimeStamp(sampleBuffer);
            CGFloat pts = CMTimeGetSeconds(ptsTime);
            [self->x264encoder encoding:pixelBuffer timestamp:pts];
        }
    });
}

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以上，则实现了iOS下使用FFmpeg+x264进行软编码的整个流程。
demo：https://github.com/XuningZhai/VideoEncode_x264